The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hybrid powertrains typically include an internal combustion engine (ICE), an electric machine (EM), and one or more torque generators that provide torque to a driveline to propel a vehicle. Two types of hybrid powertrains include a full hybrid powertrain and a mild hybrid powertrain. In a full hybrid powertrain, the EM can drive the drivetrain directly, without transferring torque through a component of the ICE. In a mild hybrid configuration the EM is coupled to the ICE through an accessory drive. Torque generated by the EM is transferred to the drivetrain through the ICE. An exemplary mild hybrid powertrain includes a so-called belt alternator starter (BAS) system. In the BAS system, the EM is coupled to the ICE via a belt and pulley configuration, which drives other accessory components, such as pumps and compressors.
Powertrain torque control typically includes two torque control domains: axle torque and propulsion torque. In a mild hybrid powertrain, the propulsion torque is the output torque at the crankshaft of the ICE, which includes the EM torque contribution.
Powertrain systems also include several torque features. Each of the features affects the amount of drive torque generated at various points along the powertrain system. An upper level or global torque feature refers to a vehicle driver, who commands a desired output torque from torque source(s) or a desired axle torque based on a driver input. Exemplary driver inputs include, but are not limited to, an accelerator pedal and a cruise control system. Modern powertrain systems include additional torque features or torque requests, such as vehicle stability control systems, traction control systems, engine overspeed protection systems, transmission shift quality systems, engine and/or transmission component protection systems, and driveline component protection systems.
The torque features of a particular powertrain system may be independent and can often attempt to control the drive torque during the same time period. Because a powertrain system produces a single drive torque output at an instance in time, an arbitration system is used to determine the correct drive torque output. A control module is typically provided for arbitrating the multiple torque requests and for controlling ICE and EM systems to produce a proper output torque.